Hello, You can absolutely start with a certificate and then a diploma in French after your 12th Arts. This is a very common path, and it will definitely help you reach the B1 level. Institutions like Alliance Française are excellent for this. Your Arts stream background is not a problem at all.
However, you must understand that the B1 level is only intermediate and is not high enough for a professional career as an interpreter or translator. Those jobs require an expert C1 or C2 level. While a diploma is a great start, it is generally not considered sufficient on its own for a high-level career.
For a serious, long-term career as an interpreter, a full 3-year B.A. (Hons.) in French is the standard and most recommended path. This degree (which you are eligible for with your Arts stream, often via the CUET exam) gives you a much deeper understanding of French literature, culture, and linguistics, which is essential for professional translation and what top employers (like embassies and multinational companies) look for.
I hope you found this information helpful and for any study related queries you can ask in careers360 app, Have a great day!